The ultimate embodiment of the first extracorporeal closed-loop blood-glucose (BG) control system, or bionic endocrine pancreas (BP), is a wearable device consisting of: a continuous glucose monitor (CGM), a drug infusion pump, and a control algorithm, which autonomously issues doses on the pump based on glucose data from the CGM. We have designed and extensively tested our hormonal BP in preclinical pig studies at Boston University (BU) and in inpatient feasibility studies in pediatrics and adults with type 1 diabetes at the Massachusetts General Hospital (MGH). We have recently built the first truly wearable mobile hormonal BP and have recently received FDA approval to test it in our first outpatient transitional study. The system is built around an iPhone 4S (Apple), which runs our control algorithm and coordinates communication between a G4 Platinum CGM (DexCom) and two (insulin/glucagon) t:slim insulin pumps (Tandem Diabetes Care). We have begun our outpatient study (February, 2013), which involves 5-day experiments of continuous closed-loop control in adults with type 1 diabetes. Subjects sleep in a hotel near MGH and spend the day within a three square mile area around Boston's Beacon Hill neighborhood. They are accompanied by a nurse during the day, and by night a nurse is on call in an adjacent hotel room. Subjects provide only their weight to start the BP, which then automatically controls BG for five days. Subjects need not trigger or manually deliver any insulin bolus at any time but the BP allows them to trigger optional meal priming bolus doses that are automatically determined and adapted by the BP. Our Beacon Hill Study, as we refer to it, will conclude in June, 2013, and be followed in July and August by our Summer Camp Study, which will involve children 6-21 years old with type 1 diabetes at two diabetes camps in central Massachusetts. We have recently submitted for review our IDE application for the Summer Camp Study to the FDA and the clinical protocol to the MGH IRB and are awaiting decisions from both by the end of April. This project aims to conduct our penultimate transitional study using our wearable BP in a multi-center out- patient setting in adults with type 1 diabetes. In a randomized cross-over design, the study will enroll 48 medical center staff members with type 1 diabetes from four medical center sites. While at work, subjects will go about their normal routines. In a randomized fashion, half of the subjects will follow their usual diabetes care regimen for 12 days while the other half will be under closed-loop control by our BP for 12 days. After a two-day washout period, subjects in both groups will crossover to the other study arm. Thus, each subject will serve as their own control. Work distractions allow a realistic assessment of usual-care therapy and provide real-world challenges to our BP. Choosing subjects who work in medical centers allows for close centralized monitoring by our study staff. Our multi-center Hospital Staff Study, as we refer to it will be our last transitional study to use our current BP, and will be followed in 2015-2016 by our pivotal trial, testing our BP in its ultimate embodiment (built and validated over the next 24 months) that we intend to put forward in a pre-market approval application to the FDA in late 2016.